Physical identification data addressing method using wobble signal, wobble address encoding circuit, method and circuit for detecting wobble address, and recording medium therefor

ABSTRACT

A physical identification data (PID) addressing method using a wobble signal, a wobble address encoding circuit, a method and circuit for detecting the wobble address and a recording medium therefor. Groove address information indicating physical identification information is phase modulated using a wobble clock signal and recorded in one of the two walls of a groove track, and land address information is phase modulated using a wobble clock signal obtained by shifting the phase of the former wobble clock signal and recorded in the other wall. That is, address information is phase modulated and recorded in each track using the wobbles having a phase difference of 90° between adjacent tracks so that a sum of wobble signals from the adjacent tracks can be a quadrature phase shift keying (QPSK) signal. Therefore, more data can be recorded in the recording medium, and since an interval in which a wobble signal disappears is not caused, recovery of a wobble clock signal can be advantageously performed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. Ser. No.09/704,656, now allowed and also claims the benefit of KoreanApplication Nos. 99-48453, filed Nov. 3, 1999 and 00-15329, filed Mar.25, 2000, in the Korean Patent Office, the disclosures of which areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical recording/playback, and moreparticularly, to a physical identification data (PID) addressing methodusing a wobble signal, a wobble address encoding circuit, a method andcircuit for detecting the wobble address, and a recording medium in ahigh density optical recording and reproducing system.

2. Description of the Related Art

Information used for physical location recognition to determine alocation to which data is written on a disc in an optical recordingsystem is referred to as physical identification data (PID). Generally,PID is address information of a physical sector in a recording andreproducing medium on which data is recorded in units of sectors. Thisis essential information for recording data at a certain location on adisc and finding the location at a later time.

In other words, PID indicates address information for finding aspecified sector to record/reproduce data to/from a certain location,particularly in a recording/reproducing disc, and indicates addressinformation of a sector which is pre-mastered during manufacture of adisc regardless of the existence or non-existence of user data.Accordingly, PID is supposed to be resistant to errors and have astructure allowing fast detection in order to exactly and quickly findthe location of a sector which data will be recorded on or reproducedfrom.

Various methods of recording PID on a disc can be largely classifiedinto two methods. One method is recording physical location informationon a disc by forming embossed pits as used in a read-only optical discto allow a certain location on the disc to be detected based on theembossed pits. The other method uses a wobble signal which can beobtained by giving some changes to recording tracks on a disc at apredetermined time interval.

An area, which is provided for performing PID addressing using theformer method, that is, using embossed pre-pits, is referred to as aheader field, as shown in FIG. 1. According to a digital versatile disc(DVD) specification for rewritable discs (2.6 or 4.7 gigabytes (GB)DVD-random access memory (RAM)) version 1.0, physical locationinformation is recorded at the location of the so called header field,which comprises pre-pits, during manufacture of a substrate. The headerfield includes a variable frequency oscillator (VFO) area for a phaselocked loop (PLL), a PID area to which a sector number is assigned, anID error detection (IED) area for storing ID error detection informationand a postamble (PA) area for setting up an initial state for modulationof data recorded following the header field. In a PID addressing methodusing pre-pits, such a header field comprising embossed pre-pits isappropriately disposed at the start of a sector to allow a pickup toeasily find and move to a desired location using this information. Asector number, sector type and a land track/groove track can berecognized from the addressed information, and even servo control ispossible.

In such a PID addressing method using conventional embossed pre-pits,data cannot be recorded in areas in which pits are formed. Therefore, aproblem of a decrease in recording density in proportion to the areaswhere the pits are formed occurs.

To store a large amount of data with a high density, it is necessary toincrease a recordable area (a user data area) by decreasing a trackpitch and minimizing a non-recordable area (overhead). For this purpose,it is effective to use a wobble signal.

When forming a substrate for a recording disc, grooves are formed alongrecording tracks on the substrate to allow a certain track to be exactlytracked by a pickup even if data is not recorded on the track. Theportions other than the grooves are referred to as lands. Recordingmethods can be classified into a method of recording data on either aland or a groove and a method of recording data on both the land and thegroove. It is more advantageous to use the land and groove recordingmethod in which data is recorded on both the land and the groove as thedensity of data increases.

In addition, a method of generating a signal of a specified frequency byvarying both walls of a groove to use it as an auxiliary clock signalduring recording is used. This signal is referred to as a wobble signal.A wobble signal having a single frequency is also recorded in thesubstrate of a DVD-RAM disc.

In a PID addressing method using a wobble signal, overhead informationsuch as a PID signal can be recorded by varying a wobble signal having asingle frequency, for example, periodically varying the phase orfrequency of the wobble signal, during recording. Here, the PID signalembedded in the wobble signal is generally referred to as a wobbleaddress.

Since the conventional PID addressing method using a wobble signal usesthe variation of both walls of a groove track in which a wobble will berecorded, as shown in FIG. 2, the method can be used only in discsemploying a land recording method in which information is not recordedin groove tracks. In other words, when using changes in both walls ofeach groove track, address information of two groove tracks at bothsides of a land track can be mixed with each other, so that exactinformation cannot be obtained from the land track. Accordingly, boththe addresses of a land track and a groove track cannot be indicatedjust by using a wobble address formed in the groove track. Therefore, itis difficult to use the conventional method in discs employing a landand groove recording method in which information is recorded in bothland and groove tracks.

Although a wobble address is recorded in the side wall of a groove trackat the boundary between a land track and the groove track, informationof wobbles formed in both walls of the land and groove tracks issimultaneously read when the land and groove recording method ofrecording information in land and groove tracks is used. Accordingly, aPID signal cannot be exactly recorded or detected when using the wobbleaddressing method shown in FIG. 2.

To solve this problem, a method of recording a wobble address in onlyone wall of each groove track is proposed, as shown in FIG. 3. In thiswobble addressing method, however, since a wobble signal is generatedfrom only one sidewall of a groove track, the strength of the signaldecreases. In addition, since the same signal is read from the groovetrack and an adjacent land track, additional information fordiscriminating a land track from a groove track is required.

SUMMARY OF THE INVENTION

To solve the above problems, a first object of the present invention isto provide a new physical identification data (PID) addressing methodusing a wobble to solve an overhead problem of an addressing methodusing embossed pre-pits, and to solve a problem of a conventional wobbleaddressing method being incompatible with a land and groove recordingmethod.

A second object of the present invention is to provide a PID addressingmethod in which wobble signals are differently configured in either oftwo walls of each groove track (or each land track) so that an in-phasecomponent signal of a quadrature phase shift keying (QPSK) signal isrecorded in one of the two walls, and a quadrature component signal ofthe QPSK signal is recorded in the other wall.

A third object of the present invention is to provide a method ofdetecting address information from a recording medium in which thewobble signals of both walls of each groove track (or each land track)are differently configured so that an in-phase component signal of aQPSK signal is recorded in one of both walls, and a quadrature componentsignal of the QPSK signal is recorded in the other wall.

A fourth object of the present invention is to provide a wobble addressencoding circuit for a high density optical disc recording andreproducing system.

A fifth object of the present invention is to provide a wobble addressdetecting circuit for a high density optical disc recording andreproducing system.

A sixth object of the present invention is to provide a recording mediumin which the wobble signals of both walls of each groove track (or eachland track) are differently configured so that an in-phase componentsignal of a QPSK signal is recorded in one of both walls, and aquadrature component signal of the QPSK signal is recorded in the otherwall.

Additional objects and advantages of the invention will be set forth inpart in the description which follows and, in part, will be obvious fromthe description, or may be learned by practice of the invention.

To achieve the above objects, the present invention provides a method ofaddressing physical identification information using a wobble on anoptical recording/reproducing medium. The method includes phasemodulating first address information indicating the physicalidentification information using a first wobble signal and recording thephase modulated first address information in one of the two walls ofeither of a groove track and a land track, and phase modulating secondaddress information using a second wobble signal having a predeterminedphase relation with the first wobble signal and recording the phasemodulated second address information in the other wall.

The present invention also provides a method of detecting a wobbleaddress from an optical recording medium, in which first addressinformation indicating the physical identification information is phasemodulated using a first wobble signal and recorded in one of the twowalls of either of a groove track and a land track, and second addressinformation is phase modulated using a second wobble signal having apredetermined phase relation with the first wobble signal and recordedin the other wall, in an optical recording and reproducing system havingan optical detecting device. The method includes providing first andsecond output signals, each having an original signal component and aharmonic component, by multiplying a difference signal between radiallyhalf-divided detection signals of the optical detecting device by thefirst and second wobble signals having the predetermined phase relation,respectively; and removing the harmonic component from the first andsecond output signals and recovering the first address information andthe second address information from the corresponding original signalcomponent having a phase component.

The present invention also provides a circuit for encoding an addressusing a wobble in an optical recording and reproducing system. Thecircuit includes a provider which generates a first wobble signal and asecond wobble signal which has a predetermined phase relation with thegenerated first wobble signal; and a phase modulator which phasemodulates first address information indicating physical identificationinformation using the first wobble signal with respect to one of twowalls of either of a groove track and a land track, and phase modulatessecond address information using the second wobble signal with respectto the other wall.

The present invention also provides a circuit for detecting a wobbleaddress from an optical recording and reproducing medium, in which firstaddress information indicating the physical identification informationis phase modulated using a first wobble signal and recorded in one oftwo walls of either of a groove track and a land track, and secondaddress information is phase modulated using a second wobble signalhaving a predetermined phase relation with the first wobble signal andrecorded in the other wall, in an optical recording and reproducingsystem having an optical detecting device. The circuit includes a wobbleclock recoverer which detects a first wobble clock signal using adifference signal (a push-pull signal) between radially half-divideddetection signals of the optical detecting device and provides a secondwobble clock signal having the predetermined phase relation with thedetected first wobble clock signal; and a phase demodulator whichrecovers groove and land address information, which is first and secondaddress information, from the push-pull signal using the first andsecond wobble clock signals.

The present invention also provides a recording and reproducing mediumemploying a groove/land recording method, wherein first addressinformation indicating physical identification information is phasemodulated using a first wobble signal and recorded in one of two wallsof either of a groove track and a land track, and second addressinformation is phase modulated using a second wobble signal having apredetermined phase relation with the first wobble signal and recordedin the other wall.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail preferred embodiments thereof withreference to the attached drawings in which:

FIG. 1 is a diagram showing a physical identification data (PID)addressing structure using conventional embossed pre-pits;

FIG. 2 shows a conventional example in which wobbles are recorded ingroove and land tracks;

FIG. 3 is a conventional example in which a wobble address is recordedin one wall of a groove track;

FIG. 4 is a diagram showing a PID addressing structure in which a wobbleaddress is recorded according to the present invention;

FIG. 5 is a diagram showing waveforms of a wobble signal in land andgroove tracks in the structure shown in FIG. 4;

FIG. 6 is a diagram showing a track structure in which a mirror or awobble synchronizing signal for synchronizing the phases of wobblesignals at an initial stage is recorded according to the presentinvention;

FIGS. 7A through 7C show an example of the contents of the PIDaddressing structure shown in FIG. 4;

FIG. 8 is a diagram showing a sector mark located at the beginning of asector and a first sector mark of a track as an example of the trackstructure shown in FIG. 6;

FIGS. 9A through 9E are diagrams showing examples of the contents of thesector mark shown in FIG. 8;

FIG. 10 is a circuit diagram of a wobble address encoding circuitaccording to an embodiment of the present invention;

FIG. 11 is a circuit diagram of a wobble address detecting circuitaccording to an embodiment of the present invention; and

FIGS. 12A through 12M are waveform diagrams showing the waveforms ofmembers of the detecting circuit shown in FIG. 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a physical identification data (PID) addressing methodusing a wobble signal, a wobble address encoding circuit, a method andcircuit for detecting the wobble address, and a recording mediumtherefor will be described with reference to the accompanying drawings,in which preferred embodiments of the invention are shown.

When reading a wobble address, which is formed using both sidewalls of agroove track, from a land track, a signal is read from the wall of eachof the groove tracks at both sides of the land track, so that thesignals from the adjacent walls of adjacent grooves are combined. Toprocess this combined signal and not allowing interference of a wobblesignal between adjacent tracks, the present invention provides a PIDstructure using a wobble, as shown in FIG. 4.

FIG. 4 is a diagram showing a PID addressing structure using wobblesallowing addresses to be independently recorded on land and groovetracks according to the present invention. This structure is applied toa disc in which physical locations on land and groove tracks are to beindividually accessed, for example, a disc employing a land and grooverecording method, in which tracks are formed to have a constant angularvelocity such as a zoned constant linear velocity (ZCLV) or a constantangular velocity (CAV) between adjacent tracks. Here, since the walls ofa groove have different shapes, it is preferable to use two beams duringmastering.

When manufacturing a substrate, grooves are formed on the substrateusing a laser beam. At this time, a wobble signal is formed bydisplacing the laser beam by the size of the wobble signal in adirection perpendicular to a tracking direction. Wobbles havingdifferent shapes for either wall of a groove, as embodied in the presentinvention, cannot be formed with a single beam. Accordingly, it ispreferable to use two beams to form different wobbles in either wall ofa groove. Alternatively, a beam having a diameter much smaller than thewidth of a track may be displaced by a desired track width in adirection perpendicular to a tracking direction. However, it isdifficult to obtain a beam having a diameter sufficiently smaller thanthe width of a track when the width of the track is narrower for highdensity recording.

The wobble signals of both walls of a groove track are differentlyconfigured to each other so that an in-phase component signal of aquadrature phase shift keying (QPSK) signal is recorded in one of thetwo walls, and a quadrature component signal of the QPSK signal isrecorded in the other wall. A groove address is always recorded in thein-phase component signal, and a land address is always recorded in thequadrature component signal. The structure shown in FIG. 4 has adisadvantage of requiring two beams for mastering but has an advantageof simplifying a circuit for detecting a signal. Alternatively, a landaddress may always be recorded in the in-phase component signal, and agroove address may always be recorded in the quadrature componentsignal.

When an address data bit is “0”, a wobble signal having a phase of 0degrees is recorded, and when an address data bit is “1”, a wobblesignal having a phase of 180 degrees is recorded. In one embodiment, forthe phase of a wobble clock signal, a carrier having a phase of 0degrees may be used for one wall of a groove track, and a carrier havinga phase shifted by 90 degrees may be used for the other wall of thegroove track.

A groove address having an in-phase component and a land address havinga quadrature component, which are recorded in either wall, respectively,of a groove track, are bi-phase shift keying (BPSK)-modulated signals. Asignal read from each track is a QPSK-modulated signal in whichmodulated groove address information in an in-phase component iscombined with modulated land address information in a quadraturecomponent.

In other words, an in-phase component signal W_(I) of QPSK recorded inone of the two walls of a groove track can be expressed as follows.w _(I) =a(nT)−sin(ωt)where T is the sample period of address data, and a(nT) has an addressvalue “1” or “−1” in a period T depending on each bit value of grooveaddress data. The variation period T of the address data exceeds theperiod 1/f of the wobble signal. Here, f is the frequency of the wobblesignal, and ω=2πf.

A quadrature component signal W_(Q) of QPSK recorded in the other wallof the groove track can be expressed as follows.W _(Q) =b(nT)cos(ωt)  (2)where b(nT) has an address value “1” or “−1” in a period T depending oneach bit value of land address data.

As described above, when wobble signals are differently configured ineither wall of each groove track, the structure of the wobble signal ofeach track can be expressed as follows.W _(track) =a(nT)·sin(ωt)+b(nT)·cos(ωt)  (3)

Meanwhile, it is very important to detect the initial phase of a wobblesignal. Accordingly, it is preferable to record a mirror zone or asynchronizing signal which can synchronize the phases of wobble signalsin each sector or in each specified unit, as shown in FIG. 6. This willbe more fully described in FIGS. 8 and 9. Additionally, in the case of acomplementary allocated pit address (CAPA) method used in DVD-RAMs, aCAPA signal and a variable frequency oscillator (VFO) embedded in theCAPA signal can be used as a reference phase signal for a wobble signal.

When detecting a wobble address from a groove track in which PID isaddressed using a wobble, a phase-modulated push-pull signal ismultiplied by a carrier, that is, a wobble clock signal to detect thephase component of an original signal (address data). In other words,when a phase-modulated signal is multiplied by a carrier, an originalsignal expressed as a direct current (DC) term and a harmonic componentwith a doubled frequency are generated.

A groove address is recovered from a wobble signal, which is recorded ona groove track as expressed by Equation (3), by multiplying the wobblesignal by a carrier, sin(ωt), as shown in Equation (4), low passfiltering the multiplied result, and removing a harmonic component fromthe filtered result to detect an original signal component.$\begin{matrix}{{{{a({nT})}{{\sin\left( {\omega\quad t} \right)} \cdot {\sin\left( {\omega\quad t} \right)}}} + {{b({nT})}{{\cos\left( {\omega\quad t} \right)} \cdot {\sin\left( {\omega\quad t} \right)}}}} = {{\frac{1}{2}{a({nT})}} - {\frac{1}{2}{{a({nT})} \cdot {\cos\left( {2\omega\quad t} \right)}}} + {\frac{1}{2}{{b({nT})} \cdot {\sin\left( {2\omega\quad t} \right)}}}}} & (4)\end{matrix}$

A land address is recovered from a wobble signal, which is recorded on agroove track as expressed by Equation (3), by multiplying the wobblesignal by a carrier, cos(ωt), as shown in Equation (5), low passfiltering the multiplied result, and removing a harmonic component fromthe filtered result to detect an original signal component.$\begin{matrix}{{{{a({nT})}{{\sin\left( {\omega\quad t} \right)} \cdot {\cos\left( {\omega\quad t} \right)}}} + {{b({nT})}{{\cos\left( {\omega\quad t} \right)} \cdot {\cos\left( {\omega\quad t} \right)}}}} = {{\frac{1}{2}{a({nT})}{\sin\left( {2\omega\quad t} \right)}} + {\frac{1}{2}{b({nT})}} + {\frac{1}{2}{b({nT})}{\cos\left( {2\omega\quad t} \right)}}}} & (5)\end{matrix}$

Since the shape of a wobble formed on one wall of each track isdifferent from that of a wobble formed on the other wall of each track,and the phase difference between these different wobbles is 90°, awobble signal read from each track spontaneously becomes a QPSK signal.Therefore, land address information and groove address information canbe detected by using an appropriate wobble clock signal (sin(ωt) orcos(ωt)).

In addition, when the period of address information with respect to thatof a carrier is synchronized in a simple ratio such as 1:1 or 1:2, asynchronous detection method of simply detecting the phase of a signalcan be used. The synchronous detection method extracts the phase of asignal by multiplying a phase-modulated signal by a carrier and thendetecting only the size of a signal at a predetermined time interval,instead of low pass filtering the signal. Such a method of detecting aPSK signal is widely known, and thus a detailed description thereof willbe omitted.

The PID structure of a wobble signal using the variation in both wallsof a groove track according to the present invention will now be morefully described.

It is preferable that address information on a single sector is repeatedthree times or more. For PID information, the amount of addressinformation to be processed is much smaller than the size of the errorcorrection code (ECC) block of usual user data so that ECC efficiencydecreases and the possibility of erroneous correction increases.Accordingly, it is more effective to repeatedly record PID informationthan to increase the number of bits for error correction. It is typicalto use an error detection code (EDC) for error correction of addressinformation.

In the case of recording PID information by loading the PID informationon a wobble by way of phase modulation according to the presentinvention, when a wobble signal is made to have a regular period, thephysical length of a sector increases as the size of the sectorincreases, so that more periods of a wobble signal can be recorded.Accordingly, the size of the PID information increases. On the otherhand, when the size of a sector is too large, the minimum recording unitof data also becomes too large, resulting in inefficiency.

It is preferable that the size of a sector is as close to the size of anECC block as possible. An ECC processing unit is a minimum recordingunit. When the size of a sector is set to be smaller than the size of anECC block, all sectors constituting an ECC block including a sector, inwhich information will be recorded or modified, should be read, and,after recording/modification of data, ECC information should be updated.As described above, a recording process requires a complexread-modify-write procedure.

For reference, existing 4.7-GB DVD-RAMs are composed of 32-kilobyte(Kbyte) ECC blocks and 2-Kbyte sectors. The length of the recordablefield of a sector is 41072 channel bits.

However, it is preferable to increase the size of a sector used in4.7-GB DVD-RAMs for high density recording. In the case of high densityrecording, the size of a correctable error decreases compared to theexisting 4.7-GB DVD-RAMs when the size of an ECC processing unit is notincreased, so it is preferable to increase the size of the ECCprocessing unit to ensure that the size of a correctable error is thesame as that required in the existing 4.7-GB DVD-RAMs. Accordingly, itis preferable to increase the size of a sector to, for example, 4, 8 or16 Kbytes. When the size of a sector is set to 4 Kbytes, and whenexisting overhead information is maintained as it is, the number ofchannel bits per sector is 82144.

When the period of channel data to be recorded is represented by Ts, theperiod of a wobble signal is represented by Tw, and the period of PIDdata is represented by Tpid, and the following description concerns theeffects resulting from changes in these periods.

The period Ts of channel data determines a recording density on a disc.As the period Tw of a wobble signal increases, the frequency of thewobble signal decreases, and the wobble signal closes to or invades theband of a servo signal such as a tracking error signal. On the otherhand, as the period Tw of a wobble signal decreases, the frequency ofthe wobble signal increases, and the wobble signal closes to or invadesa radio frequency (RF) signal band at which user data is recorded.Accordingly, it is essential to appropriately set the band of a wobblesignal. In the present invention, the period Tw of a wobble signal islarger than 50Ts and smaller than 450 Ts (50 Ts<Tw<450 Ts). Forreference, the period Tw of a wobble signal is set to 186 Ts in 4.7-GBDVD-RAMs.

The period Tpid of PID data determines the bandwidth of a modulatedsignal when the PID data is modulated using a wobble carrier. When theperiod Tpid of PID data is the same as the period Tw of a wobble signal(Tpid=Tw), and when the frequency of the wobble signal is represented byfw, the bandwidth of the modulated signal is 2fw. When the period Tpidof PID data is double the period Tw of a wobble signal (Tpid=2Tw), andwhen the frequency of the wobble signal is represented by fw, thebandwidth of the modulated signal is fw. The period Tpid of PID dataincreases, the bandwidth of a modulated signal decreases, therebydecreasing interference with peripheral signals. However, as the periodTpid increases, the efficiency of a modulated signal decreases, and theamount of recordable PID data decreases. Accordingly, it is preferablethat 1.5TwTpid<8Tw.

FIGS. 7A through 7C are diagrams showing an example of the contents of awobble PID according to the PID addressing structure of FIG. 4. As shownin FIG. 7A, a PID unit comprises a wobble sync having synchronizationinformation for determining the start position of a wobble PID signal, awobble carrier comprising a pure wobble signal not including the PID, aPID which is phase-modulated using a wobble carrier having addressinformation, and an EDC. Here, the position of the wobble sync and theposition of the wobble carrier are interchangeable.

It is preferable that address data (PID) is repeated at least threetimes in a sector, as shown in FIG. 7B. This is for enhancing therobustness of the address data against erroneous correction or erroneousdetection. Accordingly, it is preferable that the same PID unitincluding an address is repeated three or more times during a singlesector period.

As shown in FIG. 7C, a sector mark for indicating the beginning of aphysical sector is provided at the beginning of a sector. The sectormark includes a mirror zone (MIRROR), a track mark (TM) havinginformation on a track in which a corresponding sector is currentlylocated, and a VFO signal (VFO) for PLL of data to be recorded in acorresponding sector, for 1 wobble clock period. The mirror zone is onthe path of a recording and reproducing beam on a disc, does not haveany signal or information, and just reflects an incident beam with apredetermined reflectance. In this mirror zone, refraction due to a pit,record mark or a land/groove structure does not occur, so that an outputsignal read from the mirror zone is the strongest.

In a wobble PID structure according to the present invention,synchronization information for detecting the beginning of addressinformation (PID) and detecting the phase of a wobble carrier isprovided before the address information in order to prevent a temporaryfailure in achieving a PLL or a temporary asynchronous clock phase frominfluencing adjacent address information. It is preferable thatsynchronization information can be detected after data demodulation aswell as when the data has been modulated. Accordingly, in the presentinvention, synchronization information for address information exists inthe form of a wobble sync using a Barker-Code which is a sort of apseudo-random sequence. A method of constructing and detecting aBarker-Code and a synchronizing signal is disclosed in U.S. Pat. No.5,511,099, entitled “Passband Sync Block Recovery” and issued to thepresent applicant, and thus a detailed description thereof will beomitted.

In addition, for data modulated by way of QPSK, various methods, such asa method of recording a burst signal having only a carrier of a fixedperiod and a method of recording a carrier signal in a pilot tone, areproposed to easily detect a carrier. Particularly, in the case of awobble PID, it is preferable to insert a burst signal having only awobble carrier signal at a predetermined interval since it istechnically difficult to insert a carrier using a pilot tone method. Thepilot tone method is proper when it is applied to systems rarely havinga change in frequency. However, it is difficult to equally maintain thephase characteristic of a band pass filter for extracting a pilot tonein systems having changes in frequency due to accompanying mechanicaldevices so that an exact phase cannot be detected.

FIG. 8 is a schematic diagram showing the shapes of a sector marklocated at the beginning of a sector and the first sector mark of atrack, in the track structure shown in FIG. 6. FIG. 8 shows a firstsector mark (a zero sector mark or a reference sector mark), which islocated at a transition position from a groove track to a land track orfrom a land track to a groove track, that is, at the beginning of atrack, and a sector mark located at the beginning of a sector. Sectormarks are provided to land tracks as well as groove tracks and havedifferent structures in odd tracks and even tracks. The first sectormark of a track has a different structure from the other sector marks ofthe track.

The sector mark indicates whether a current track to be written to orread from is an even or odd track, and indicates the start point of thecorresponding track.

As shown in FIG. 9A, the sector mark of an even groove track or an evenland track includes a mirror zone, a track mark and a VFO signal. Asshown in FIG. 9B, unlike the sector mark of an even groove track or aneven land track, the sector mark of an odd groove track or an odd landtrack includes a mirror zone instead of a track mark. That is, thesector mark of an odd groove track or an odd land track sequentiallyincludes a mirror zone, another mirror zone and a VFO signal. The sectormark of an even track shown in FIG. 9A may be the sector mark of an oddtrack shown in FIG. 9B, and the sector mark of an odd track shown inFIG. 9B may be the sector mark of an even track shown in FIG. 9A.Another modification is also possible.

As shown in FIG. 9C, the first sector mark of an even track, which hasinformation on a reference sector indicating the beginning of a track,includes a mirror zone and a track mark in addition to the structure ofthe sector mark of an even track (FIG. 9A). That is, a mirror zone,track mark, mirror zone, track mark and a VFO signal are sequentiallyarranged.

As shown in FIG. 9D, the first sector mark of an odd track includes amirror zone and a track mark in addition to the structure of the sectormark of an odd track (FIG. 9B). That is, a mirror zone, track mark,mirror zone, mirror zone and a VFO signal are sequentially arranged. Thefirst sector mark of an even track shown in FIG. 9C can be interchangedwith the first sector mark of an odd track shown in FIG. 9D, and anothermodification is also possible.

FIG. 9E shows a sector mark (SM) and PID structure when each track has msectors. Sector marks are provided to not only groove tracks but alsoland tracks, and a PID unit is repeated three times in each groovetrack.

The following description concerns the generation and detection of awobble signal using variation in both walls of a groove track accordingto the present invention.

FIG. 10 is a circuit diagram of a wobble address encoding circuitaccording to an embodiment of the present invention. The wobble addressencoding circuit includes a wobble signal generator 100, a phase shifter102, and PSK modulators 104 and 106.

In FIG. 10, the wobble signal generator 100 generates a wobble signalhaving a predetermined wobble frequency fw. The phase shifter 102 shiftsthe phase of the wobble signal generated by the wobble signal generator100 by 90° to generate a phase shifted wobble signal.

The PSK modulator 104, which can be manifested as a multiplier,multiplies groove address data of “1” or “−1” by the wobble signalgenerated by the wobble signal generator 100. Therefore, aBPSK-modulated signal obtained by multiplying groove address data by acarrier having a phase of 0°, that is, sin(ωt), is recorded in one ofboth walls of a groove track.

The PSK modulator 106, which can be manifested as a multiplier,multiplies groove address data of “1” or “−1” by the phase shiftedwobble signal generated by the phase shifter 102. Therefore, aBPSK-modulated signal obtained by multiplying land address data by acarrier having a phase of 90°, that is, cos(ωt), is recorded in theother wall of the groove track.

FIG. 11 is a circuit diagram of a wobble address detecting circuitaccording to an embodiment of the present invention. The wobble addressdetecting circuit includes an optical detecting device 200, a subtractor202, a band pass filter (BPF) 204, a phase locked loop (PLL) circuit206, a phase shifter 208, multipliers 210 and 212, and low pass filters(LPFs) 214 and 216.

The subtractor 202 detects a difference signal (a push-pull signal)between the radially half-divided output signals of the opticaldetecting device 200 which can be manifested as a photodiode. Here,address information is detected from the push-pull signal.

The BPF 204 band filters the push-pull signal. The PLL circuit 206detects a wobble clock signal from the output of the BPF 204. The phaseshifter 208 shifts the phase of the wobble clock signal detected by thePLL circuit 206 by 90° to provide a phase shifted wobble clock signal.

In the case of a BPSK signal or a QPSK signal, a section in which asignal is 0 does not exist during recovery of a wobble clock signal.When the PLL circuit 206 performs full-wave rectification on the pushpull signal and obtains a 2-multiple-speed clock signal, a nearlycomplete clock signal can be detected. The PLL circuit 206 detects thewobble clock signal by recovering and half-dividing a 2-multiple-speedwobble clock signal. However, a phase synchronizing signal is requiredfor the 180°-phase of the 2-multiple-speed clock signal in order tosolve an ambiguity problem. Accordingly, the wobble sync and the wobblecarrier signal shown in FIG. 7A and the VFO signal recorded in thesector mark shown in FIG. 8 are used.

The multiplier 210 multiplies the band-filtered push-pull signalprovided by the BPF 204 by the wobble clock signal provided by the PLLcircuit 206. Then, an original signal expressed as a DC term and amultiplied harmonic component are generated. That is, an original signal(groove address data of an in-phase component) and a doubled harmoniccomponent are generated in a groove track, as shown in Equation (4).

The multiplier 212 multiplies the band-filtered push-pull signalprovided by the BPF 204 by the 90□-phase shifted wobble clock signalprovided by the phase shifter 208. Then, an original signal expressed asa DC term and a multiplied harmonic component are generated. That is, anoriginal signal (land address data of a quadrature component) and adoubled harmonic component are generated in a land track, as shown inEquation (5).

The LPF 214 filters the harmonic component of the output of themultiplier 210 to detect an original signal component (a phasecomponent). The LPF 216 filters the harmonic component of the output ofthe multiplier 212 to detect an original signal component. In otherwords, groove address information is provided from the LPF 214 in agroove track, and land address information is provided from the LPF 216in a land track.

With respect to a generated wobble signal as shown in FIG. 5, in thestructure shown in FIG. 4, a signal shown in FIG. 12A, which is readfrom a groove track, is detected from the push-pull signal of thesubtractor 202. A signal shown in FIG. 12B, which is read from a landtrack, is detected from the push-pull signal of the subtractor 202. Asignal shown in FIG. 12C, which is read from a groove track, is detectedfrom the push-pull signal of the subtractor 202.

A signal shown in FIG. 12D is output from the multiplier 210 and is theresult of multiplying the BPSK-modulated signal of FIG. 12A read fromthe groove track by sin(ωt). A signal shown in FIG. 12E is output fromthe multiplier 212 and is the result of multiplying the BPSK-modulatedsignal of FIG. 12A read from the groove track by cos(ωt).

A signal shown in FIG. 12F is output from the multiplier 210 and is theresult of multiplying the BPSK-modulated signal of FIG. 12B read fromthe land track by sin(ωt). A signal shown in FIG. 12G is output from themultiplier 212 and is the result of multiplying the BPSK-modulatedsignal of FIG. 12B read from the land track by cos(ωt).

A signal shown in FIG. 12H is output from the multiplier 210 and is theresult of multiplying the BPSK-modulated signal of FIG. 12C read fromthe groove track by sin(ωt). A signal shown in FIG. 12I is output fromthe multiplier 212 and is the result of multiplying the BPSK-modulatedsignal of FIG. 12C read from the groove track by cos(ωt).

FIG. 12J shows groove address information detected from the groovetrack, which is provided through the low pass filter 214 for removing aharmonic component from the output of the multiplier 210 shown in FIG.12D. FIG. 12K shows land address information detected from the groovetrack, which is provided through the low pass filter 216 for removing aharmonic component from the output of the multiplier 212 shown in FIG.12E.

FIG. 12L shows land address information detected from the land track,which is provided through the low pass filter 216 for removing aharmonic component from the output of the multiplier 212 shown in FIG.12G. FIG. 12M shows groove address information detected from the landtrack, which is provided through the low pass filter 214 for removing aharmonic component from the output of the multiplier 210 shown in FIG.12F.

The present invention can be effectively applied to a high densityoptical recording and reproducing system.

A land track can be discriminated from a groove track according to a PIDaddressing structure of the present invention. For example, addressinformation indicating a sector number is sequentially allocated in aradial direction starting from the inside of a disc, and recorded in thewall at the boundary between a groove track and a land track, a grooveaddress modulated with a carrier having a phase of 0° is recorded in theinner wall of a groove at the inner most circumference of the disc, anda land address modulated with a carrier having a phase difference of 90°to the above carrier is recorded in a wall at the boundary between theinnermost groove and the next land. In this case, the address (sectornumber) of a land track has a larger value in a groove track, and theaddress (sector number) of a groove track has a larger value in a landtrack. In addition, a land address is extracted from a quadrature signalcomponent, and a groove address is generated from an in-phase signalcomponent so that it can be determined whether a land track or a groovetrack is read at present using the above relation.

In the present invention, not only is one address information recordedin a single area, for example, the address of a sector is recorded in anarea corresponding to the single sector in a groove track, but also theaddress of a corresponding sector in an adjacent land track can berecorded in the sector area. The address of a corresponding sector in anadjacent land track may vary with the length of the sector and thecharacteristics of a modulated signal. Through such a method, aplurality of addresses can be read while a single sector is being readso that, even if one of groove address information and land addressinformation cannot be read, the address information that cannot be readcan be inferred from the address information that is read and other discinformation.

As described above, the present invention can solve the overhead problemof a conventional PID addressing method using embossed pre-pits, and cansolve the problem that a conventional wobble address method cannot beapplied to a land and groove recording method.

In addition, the present invention records in each track, wobble addressinformation phase modulated using wobble signals having a predeterminedphase relation, that is, having a phase difference of 90° betweenadjacent tracks, so that a QPSK signal can be read from each track.Therefore, a larger amount of data can be recorded, and a short periodof a wobble signal does not cause a problem. Since a section in which awobble signal disappears does not exist, the present invention isadvantageous in recovering a wobble clock signal.

1. A method of detecting a wobble address from an optical recordingmedium, in which first address information indicating physicalidentification information is phase modulated using a first wobblesignal and recorded in one of two walls of either of a groove track anda land track, and second address information is phase modulated using asecond wobble signal having a predetermined phase relation with thefirst wobble signal and recorded in the other wall, in an opticalrecording and reproducing system having an optical detecting device, themethod comprising: providing first and second output signals, eachhaving an original signal component and a harmonic component, bymultiplying a difference signal between radially half-divided detectionsignals of the optical detecting device by the first and second wobblesignals having the predetermined phase relation, respectively; andremoving the harmonic component from the first and second output signalsand recovering the first address information and the second addressinformation from the corresponding original signal component having aphase component.
 2. The method of claim 1, further comprisingdiscriminating the land track from the groove track using a correlationbetween a size of address data on the land track and a size of addressdata on the groove track, the address data having been recovered in thestep of recovering the first address information and the second addressinformation.
 3. A circuit for detecting a wobble address from an opticalrecording medium, in which first address information indicating physicalidentification information is phase modulated using a first wobblesignal and recorded in one of two walls of either of a groove track anda land track, and second address information is phase modulated using asecond wobble signal having a predetermined phase relation with thefirst wobble signal and recorded in the other wall, in an opticalrecording and reproducing system having an optical detecting device, thecircuit comprising: a wobble clock recoverer which detects a firstwobble clock signal using a difference signal (a push-pull signal)between radially half-divided detection signals of the optical detectingdevice and generates a second wobble clock signal having a predeterminedphase relation with the first wobble clock signal; and a phasedemodulator which recovers groove and land address information, whichare first and second address information, from the push-pull signalusing the first and second wobble clock signals.
 4. The circuit of claim3, wherein the wobble clock recoverer comprises: a phase locked loopcircuit which detects the first wobble clock signal from the push-pullsignal; and a phase shifter which shifts the phase of the first wobbleclock signal by 90□ to generate the second wobble clock signal.
 5. Thecircuit of claim 3, wherein the phase demodulator comprises: a firstmultiplier which multiplies the first wobble clock signal by thepush-pull signal to a first output signal having a first original signalcomponent and a first harmonic component; a second multiplier whichmultiplies the second wobble clock signal by the push-pull signal toprovide a second output signal having a second original signal componentand a second harmonic component; a first low pass filter which low passfilters the first output signal to detect only the first original signalcomponent having the first address information; and a second low passfilter which low pass filters the second output signal to detect onlythe second original signal component having the second addressinformation.
 6. The circuit of claim 4, wherein the phase demodulatorcomprises: a first multiplier which multiplies the first wobble clocksignal by the push-pull signal to provide a first output signal having afirst original signal component and a first harmonic component; a secondmultiplier which multiplies the second wobble clock signal by thepush-pull signal to provide a second output signal having a secondoriginal signal component and a said harmonic component; a first lowpass filter which low pass filters the first output signal to detectonly the first original signal component having the first addressinformation; and a second low pass filter which low pass filters thesecond output signal to detect only the second original signal componenthaving the second address information.
 7. The circuit of claim 3,wherein the first wobble clock signal relates one of two walls of theone groove or land track of the optical recording medium, and the secondwobble clock signal relates to the other one of walls of the one grooveor land track.
 8. The circuit of claim 7, wherein the two walls storethe groove and land address information as bi-phase shift keying (BPSK)signals, respectively, and the groove and land address informationtogether result in a quadrature phase shift keying (QPSK) signal.
 9. Thecircuit of claim 4, wherein the phase locked loop circuit full waverectifies the push-pull signal and half-divides the full wave rectifiedpush-pull signal, to generate the first wobble clock signal.
 10. Thecircuit of claim 4, wherein the wobble clock recoverer further comprisesa band pass filter which band pass filters the first wobble clock signalprior to being output to the phase demodulator.